JPH0380181A - Device for producing single crystal - Google Patents

Abstract

PURPOSE:To obtain the device capable of producing a uniform and high-quality single crystal at the time of obtaining a single crystal by the vertical boat growth method by setting an auxiliary heating element capable of independently controlling its heat output inside a main heating element for heating and melting the raw material. CONSTITUTION:The auxiliary heating element 6 closer to a crucible 3 is provided inside the main heating element 5 for heating the crucible 3 to form the single crystal producing device which is practically analogous to the well- known vertical Bridgman technique. The quartz crucible 3 is placed in a susceptor 4 made of isotropic graphite in an airtight vessel 1 having a heat- resistant insulating material 2 and moved up and down by a supporting shaft 7 along with the susceptor 4. A single crystal is grown from the molten material 10 of the high-purity polycrystal GaAs as the raw material by using the crucible 3 in the hot zone. At this time, the auxiliary heating element 6 is set slightly lower than the interface A between the molten material 10 and the crystal 9, and its position is controlled over the entire crystal growth. The obtained GaAs crystal has good characteristics and is capable of greatly contributing to the production of a semiconductor device in high yield.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a single crystal growth apparatus, and particularly to a crystal growth method for obtaining a single crystal by solidifying a melt in a crucible, such as the vertical Bridgman method. The present invention relates to a single crystal growth apparatus that makes it possible to accurately form a temperature environment for obtaining high quality single crystals.

[Conventional technology]

2. Description of the Related Art Crystal growth from a melt is the main method for manufacturing semiconductor single crystals used as substrates for various semiconductor devices such as field effect transistors, Schottky barrier diodes, and integrated circuits (ICs). In the crystal growth method from a melt, it is required to precisely control the shape of the crystal growth surface (solid-liquid interface) from the start to the end of crystal growth.

In the pulling method, which is one of the methods for growing crystals from a melt, the crystal growth surface is controlled by controlling the rotation speed of the crucible, the rotation speed of the crystal, and the pulling speed.

(2) As another crystal growth method, a vertical boat growth method in which a melt is solidified as it is in a crucible to obtain a single crystal is effective.

The vertical boat growth method includes the vertical Bridgman method (VB method) and the temperature gradient solidification method (VGF method). The former VB method is a method of growing a single crystal by mechanically changing the relative position of the main heater and the crucible, while the latter VGF method is a method of growing a single crystal by mechanically changing the relative position of the main heater and the crucible. This is a method of growing single crystals by changing the temperature distribution.

This vertical Bridgman method or VGF method is suitable for manufacturing large diameter circular wafers. However, compared to the pulling method in which the growing crystal is pulled out of the melt and solidified while rotating, this boat method is characterized by static state changes, so the crystal growth surface can be adjusted by controlling the rotational speed, etc. Since this is impossible to control, the crystal growth surface has been controlled by devising a hot zone structure.

An example is shown in Figure 4 (III, 8, Gault e
t, alJ, C, G 74 (1986) 491-5
0G page). In FIG. 4, a melt 10 is prepared in a crucible 3a, and an inorganic compound semiconductor (hereinafter referred to as rm- v
solidify a single crystal of a group compound semiconductor (crystal 101.S high growth method (e.g. vertical Bridgman method, etc.)
In this case, a groove 1 is formed in the susceptor 4a that holds the crucible 3a.
This is an example in which an attempt was made to control the thermal environment and heat flow near the susceptor 4a. The arrows in FIGS. 5(a) and 5(b) indicate the heat flow in the early and late stages of crystal growth, respectively. By using the susceptor 4a provided with the grooves 12, it is possible to control the dissipation of heat from the crystal at the initial stage of crystal growth. That is, by providing a groove serving as a heat insulating part in the susceptor, the heat flow in the lateral direction of the heat flow passing through the susceptor can be suppressed, and the heat flow in the lateral direction of the crystal can be controlled. However, in the method of controlling heat flow using such a susceptor provided with grooves, the effect is naturally limited to the vicinity of the susceptor, and becomes significantly smaller at locations away from the susceptor. As shown in Figure 5(b), in the late stage of crystal growth away from the susceptor, (4
) Figure 5 (Compared to a>, there is almost no effect of the grooved susceptor, and there is also a large heat flow in the lateral direction, and there is a large difference in the heat flow passing through the crystal growth surface between the early and late stages of crystal growth.) .

By the way, in crystal growth from melt, the shape of the crystal growth surface is largely dependent on the heat flow near the crystal growth surface, and in order to control the shape of the crystal growth surface, it is necessary to control the heat flow throughout the entire crystal growth. is necessary.

In crystal growth using the above method, it is difficult to control heat flow in the latter stages of crystal growth, and there is a strong desire for a method of controlling heat flow throughout crystal growth in order to improve crystal quality.

[Problem to be solved by the invention]

In crystal growth from melt, precise control of the crystal growth plane throughout the crystal growth is essential to obtain uniform, high-quality crystals. It is necessary to precisely control the heat flow passing near the surface (solid-liquid interface) (5).

However, it has been difficult to solve the above problems with conventional methods.

An object of the present invention is to provide a single crystal manufacturing apparatus for manufacturing a uniform and high quality single crystal.

[Means to solve the problem]

According to the present invention, the above problem is solved by a vertical bridge in which a seed crystal is housed in the bottom of a vertically arranged crucible, a raw material is filled above the crucible, the raw material is heated and melted, and the melt is solidified to obtain a single crystal. In a single crystal manufacturing apparatus for carrying out the Mann method or the VGF method, an auxiliary heating element is provided inside the main heating element that heats and melts the raw material, and the amount of heat generated can be controlled independently of the main heating element. The problem is solved by a single crystal production apparatus characterized by the following.

The above-mentioned auxiliary heating element has a mechanism that allows the relative positional relationship between the heating part and the crystal growth surface to be controlled from the start to the end of crystal growth. (6) is preferable in controlling the shape of the interface).

[For production]

According to the present invention, by providing an auxiliary heating element in addition to the main heating element around the crucible, the heat flow within the crystal body can be controlled, so that a single crystal with less distortion can be obtained.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a schematic longitudinal cross-sectional view of a vertical Bridgman method single crystal manufacturing apparatus showing one embodiment of the present invention, and FIG. 2 is a schematic diagram for explaining heat flow during crystal growth according to the present invention. be.

As shown in FIG. 1, the single crystal production apparatus of the present invention is similar to the known vertical Bridgman method, but an auxiliary heating element is placed closer to the crucible inside the heating element that melts the raw material in the crucible. The difference is that they are provided.

(7) In the single crystal device of the present invention, a crucible 3 made of quartz with an outer diameter of 800 mm and a height of 150 mm is placed inside a susceptor 4 made of isotropic graphite in an airtight container 1 having a heat insulating material 2 such as graphite felt. Then, the crucible 3 is moved up and down together with the susceptor 4 by the support shaft 7.

In addition to the conventional main heating element 5, an auxiliary heating element 6 was provided on the side of the crucible.

The heating element is made of isotropic graphite, and the height of the main heating element 5 is 2.
0 cm, and the height of the auxiliary heating element 6 was 4 cm.

Crystal growth was performed in the hot zone using a quartz crucible with an outer diameter of 80 mm and a height of 150 mm. The raw material is high purity GaAs polycrystalline IL, 5 kg, 820330
0 g was used.

After melting the raw materials, the growth rate was 3 mm/in an argon atmosphere of 7 atm.
It was possible to grow crystals with a diameter of 3 inches.

FIG. 1 is a diagram during crystal growth, showing a seed crystal (GaAs) 8, a crystal 9, and a raw material melt 10 from the bottom inside the crucible, and a sealing material 11 is placed on top of them.

(8) The auxiliary heating element 6 is positioned over the entire crystal growth so that it is slightly below the interface (solid-liquid interface) A between the raw material melt 10 and the crystal 9, as shown in an enlarged view in FIG. controlled.

FIG. 3 is a diagram showing changes in the amount of heat generated by the heating element during crystal growth according to the present invention. As the crystal growth progresses, heat radiation from the solidified crystal increases, so in order to cancel the heat radiation from the sides, By increasing the amount of heat generated by the auxiliary heating element and controlling the amount of heat near the crystal growth surface, we were able to achieve stable crystal growth.

[Effects of the Invention] As an evaluation of crystallinity, the dislocation density in the (100) plane was measured.

As explained above, according to the present invention, the obtained GaAs
In the crystal, the region in which the etch pit density (BPD) in the (100) plane exceeds 2 XIO' cm-2 was reduced over the entire crystal. Moreover, the average value of EPD within the plane is approximately 1 × 10
'cm-2, which is less than 115 that of GaAs single crystal (9) produced by the conventional pulling method, making it possible to greatly contribute to the manufacture of semiconductor devices with good characteristics and high yield.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a vertical Buri-Fujiman single crystal production apparatus showing one embodiment of the present invention, and FIG. 2 is a schematic diagram for explaining heat flow during crystal growth according to the present invention. 3 is a diagram showing the change in the calorific value of the heating element during crystal growth according to the present invention, FIG. 4 is a schematic vertical cross-sectional view for explaining the conventional example, and FIG. 5(a) and (b) are conventional schematic diagrams showing the heat flow at the initial stage and the latter stage of crystal growth, respectively. 1... Airtight container, 2... Heat insulating material, 3...
- Crucible, 4... Susceptor 5... Heating element, 6... Auxiliary heating element, 7... Support shaft, 8... Seed crystal, 9... Crystal,
10... Raw material melt, 1■... Sealing material,
12...Groove. (10) 1st Figure 6... Auxiliary heating element diagram JP-A-3-80181 (5)

Claims (1)

[Claims] 1. A seed crystal is housed at the bottom of a vertically arranged crucible;
In a single crystal manufacturing apparatus for carrying out a vertical boat growth method in which a raw material is filled above the raw material, the raw material is heated and melted, and the melt is solidified to obtain a single crystal, the main heat generating device heats and melts the raw material. 1. A single-crystal manufacturing apparatus, characterized in that an auxiliary heating element is installed inside the main heating element, and the amount of heat generated can be controlled independently of the main heating element. 2. The auxiliary heating element is characterized in that it has a mechanism capable of controlling the relative positional relationship between the heating part and the crystal growth surface from the start to the end of crystal growth. A single crystal manufacturing apparatus according to claim 1.